Alloy steel



Patented Mar. 14,1939 I v I i nyramn-n. Saklatwalla, 5

N a z- Application March.12,1937; f SerlalNo.130,515 H 3 Claims. (01'. s -125 This invention relates 'to alloy steels and parsimultaneouslypresent or not, such steels display ticularly to alloysteels containing a high silicon a very low degree of corrosion resistance. content combined with copper and phosphorus, Silicon has been used as a corrosion-resisting and 'especially containing carbon in the lower element in steel generally in conjunction with 5 ranges of carbon content of steels; anotherelement such as chromium. If silicon is 5 This application is a continuation in partof utiliz edfalone 'for this purpose, the percentages. myappplications serial Nos; 50,928,- filed Novemrequired for bringing about corrosion resistance ber 21, 1935, and 701,23l,'fi1ed December 6, 1933. are so high as' to cause the resultant steelto be The main object of myinvention is to produce hard, brittle and practically incapable-of fabrica- 0 by the use of very cheap alloying elements an tion'by the ordinary p rocesses. 'Silic'on is utilized alloy steel containing low amounts of alloying elein'the manufacture of all steels as a deoxidizing ments and possessing a corrosion resistance to agent and certain residual, P a sbf it are mild corroding media, such as the atmosphere; left in the steel as insurance of complete de' Another object of my invention is to produce oxidation. In other cases, as in silicon-structural such steels of comparatively low carbon content steelsja higher percentage is intentionally left 15 obtaining the strength properties in the steel or added to impart strength. In the ordinary principally-from the alloy content and thus ob-' steels the contents of residual silicon left from viating the lack of'du'ctility' and other deleterious deoxidation vary from approximately .15% -to properties which are :introduced when strength 35%. when silicon is added as the stren then is. obtained"in' steels by merelyincreasing the ing alloying element, its contentgenerally runs 20 carbon content; I I up higher than 35%, even up to- 1%. Even with Alloy steels resistant to corrosion are produced such silicon percentages the steel displays some by the use of elementssuch as chromium, tung degree ofbrittlenes's,; coarse structure and desten, cobalt, aluminum, titanium, nickel and the c eased w d l co p d to Carbon S v f like, which are comparativelyexpensive, and rethe same strength. Such steels, up to even 1% quire appreciable contents of such elements to be ofsilicon, however, do not possess any appreciable present'in the steel to obtain corrosion resistance, corrosion resisting properties. On the contrary,- Very many of the above enumerated elements n s c depending pon Contents 0 have the further disadvantage that they are the other elements, such ascarbon, sulphur, andreadily oxidizable in the processes of steel max: anganese. e a, it has bee laimed t atsuch a 30 ing and therefore a considerable loss of values Silicon content, i t, accelerates-atmospheric occurs when'the scrap containing suchelements' corrosion. v I a i 1 is remelted for the production of newsteel; By t e COmPOSRiOYL Of y invention I v Further, comparatively cheap alloy steels are obv efi enumerated deficiencies 5 produced by the introduction in the steel of cop have el minated thehigh cost of exp v 5 per. either' alone or together with slight perrosionresistant elements. Further, I have centages of phosphorus. Such steels, in order to brought about the corrosionresistance by. theuse display any appreciable resistance, for instance of comparatively verysmall percentages of each to atmospheric corrosion, have to contain an the y e s 15am advantage 4o appreciable amount of copper, even up to apas itis recognized that steels of low alloy content 40 proximately 1% Whether slight amounts of are more uniform and reliable in properties. By phosphorus are added to such copper steel or not, e, m ina ion of Silicon, and copper in the it iswell known that such steel has the objeo} presence o phosphorus Ill-bring about a considtionable property of 'being very diiiicultly rolled, 'f degme of corroslon' reslstaeqe \wlthout formed and fabricated. Such steels are especially gomg to i high, el/ of slhcon or of objectionable where the steelin the processes of coppier' 'wlth g t f f deleterious manufacturing has to be heatedto a high temphyslcal proper 'slmi y I have been able to r'ature and allowed to cool. It is well known name h corrosion resisting properties of; De fairly high phosphorus content without intro-,- h h such 'appreclable percentage? o 1 ducing the well known deleterious effects of phosper are present in the steel, such steel is subJect yphorus I accomplish thislbythe Combined use-OI to Prwmwtwn e n Wh en.the amounts of "silicon and copper. in the right -proportions, in pp 'i 110W, Such, r mstancflfls n conjunction 'with the phosphorus. .I have also in t e r c e -b a in steels, a .found that by maintaining the carbon percentbetween 20% and 30%, whether phosphorus is ages in the lowerranges of steel, namely, approx- 55 imately between .01% and 25%, I can produce silicon-copper-phosphorus s t e el s, possessing ample strength as well as ductility, without the deleterious effects of a high carbon content such as propensity towards lack of impact strength or reduced ductility. Further, the combination of elements of my invention produces a steel which is readily weldable by the ordinary processes of welding].- v f I have found that by the proper combination of silicon with copper and phosphorus within certain limits of each of these elements, together with definite limits of the carbon content, very useful corrosion resistant steels suitable for general purposes can be obtained at a reasonable cost. I have found that, in order to obtain high tensile steels with a high degree of ductility and corrosion resistance, together. with resistance to shock and a good degree of weldability, the elements silicon, copper, phosphorus and carbon are required to be within the'following limits:

Per cent Silicon 1.10 to 1.65 Copper -4 .15 to .60 Phosphorus 1.10to .22 Carbon .Olto ;25

While useful steels are obtained in .thefabove ranges of elements, I have found that. steels with particularly good strength and ductility, together with corrosion resistance, are obtained when the alloying elements and carbon are kept within the following ranges:

, V Per cent Silicon I 1.20 to 1.35 Copper .30 to .45 Phosphorus .12 to .15 Carbon -i i .07 to .12

Besides the property of resistance to corrosion from the atmosphere, and from other mild corroding media, I have found that my steels containing silicon, copper, and phosphorus are also resistant to the action'of high temperatures'and possess comparatively higher strength and resistance to scaling than carbon steels of'equivalent strength properties. These useful properties at high temperature are derived without the use of expensive elements, such as chromium, tungsten and the like which'are commonly incorpo ratedin steels usedat high temperatures.

For resistance to mild corrosion, such asthe atmosphere, when copper aloneis used it is found. that thepercentage required to bring about any the copper precipitates in a finely divided form and thus precipitation hardening of the steel sets in. The addition of phosphorus to the copper steel augments the corrosion resistance but does not materially offset the mechanical difficulties encountered by the'high copper content.

Such percentages of copper raise the yield point of the steel but do not materially impart'strength if the carbon content is low, such as between .06% and .12%. For producing the requisite strength, therefore, the carbon content has to be appreciably raised, which is an undesirable feature, as it is well known that the physical deficiencies of .high copper content are accentuated by the presas the presence of phosphorus accentuates the brittleness due to silicon if some other offsetting element, such as copper, is not present.

I have found that when I combine silicon in the broader range given above, namely, between 1.10% and 1.65%, with a copper range of .15% to .60% and phosphorus from .10% to .22% I can bring about corrosion resisting properties in such steel without showing the deficiencies either of .a high copper or of a high silicon content. I,

further, achieve a corrosion resistance in the steel much greater than would beobtained by, say, 1% copper alone or together with phosphorus or by, say, 3% silicon. At the same time I utilize the corrosion resistant properties of the cheap element phosphorus offsetting its deleterious effects. I have found that I can introduce'in this combination of silicon and coppera phosphorus content ,of between .10% and 20%, which is -much higher than the phosphorus content found in ordinary commercial steels. It-is well known that when a steel contains'a high percentage of phosphorus, such as the above, it becomes brittle and particularly so at low temperatures. I have found that in the presence of the above combination of silicon and copper such deleterious properties due to phosphorus arenot present. but that the corrosion resistance ofthe silicon-copper combination is very considerably increased by the phosphorus content. I have further found that. the phosphorus helps to augment the useful strength of the steels and therefore enables such steels to be produced with very low carbon contents comparatively. to their strength.

I have found that strength is obtained in the steels of my above combination with comparatively low carbon contents. This is a great advantage particularly in steels which contain silicon, copper, and phosphorus. It is well known that when silicon, copper or phosphorus .are present individually in steel that the higher the carbon content. of such steel the more. pronounced are the deleterious properties due tothese elements. While such deleterious properties of the individual elements are offset by a proper balancing of the elements in my combination, the deleterious properties of each of the elements being suppressed by the presence of the one or combination of two of the other elements, nevertheless it is advantageous, to keep low the presence of an element like carbon which is known to produce deleterious effects in the presenceof the individual elements.

A further advantageous feature of my invention is the fact that in counteracting. thebrittleness due to the high silicon content I use an element such as copper, which augments at the same time the corrosion-resistant property of the silicon. Further the combination of silicon and copper counteracts the deleterious properties of thephosphorus at the same time taking advanta'ge of its corrosion and heat resisting'properties. The combination, therefore, permits the full play of the corrosion resistant and the heat resistant the added advantage that the elements used are all obtainable at a very cheap cost and are elements which are available and used in any ordinary steel making operation.

In the composition of my steel, besides the good physical properties,

elements, such as nickel, tungsten, titanium, va-

nadium, zirconiumaluminum and the like. Such elements, however, can be present in small amounts, to fractions'of a percent, without af-- fecting the properties of my steel. Manganese and sulphur may be present in the amounts usual- 1y found in common steels, although I prefer to have not over about ,5 manganese and not over about .05% sulphur.

The steels of my invention can bemanufactured by the ordinary steel making processes, such as the Bessemer, open hearth, crucible or electric furnace process. The siliconcontent can be introduced in the usual manner by the use of ferro-silicon of the percentages commonly available in commerce. The ferro-silicon may be added in the furnace, but it is desirable to add some in the form of a high percentage ferro-silicon, such as or in the ladle in order to obtain a more accurate final content of silicon in the steel. The copper may be added in the furnace, and small additions for final'correction be made in the ladle. The added in the form of ferrophosphorus or may be partly derived from the phosphorus content of some oi'the ingredients used in melting and refining the steel. Part of the form-phosphorus maybe added in the furnace and then the restadded in the ladle to obtain more definite control of the analysisof the finished steel. Owing to the rapid oxidizability'oi of the analysis may phosphorus may be the ranges given. Furthe corrosion resistance is brought about by the balanced percentages of I produced in the phosphorus it is recommendable to add the main bulk, if not all, of the form-phosphorus in the ladle. In the casting, rolling and other fabricating operations of the steel the behavior of my composition is not any different to that of usual steels of equal physical properties.

The steels of my composition possess the physical properties of strength, ductility, weldability, etc., in the as-rolled condition, but they are capable of heat treatment to develop and produce necessary different properties in particular cases. The steels of my composition are capable of being v forms of all the ordinary products usually produced by steel works. They can be fabricated into billets, slabs, bars, rods, plates, shapes, sheets, tubes, wire and the like.

While I have specifically described the preferred embodiment of my invention, the invention may be otherwise embodied and practiced within the scope of the following claims.

I claim:

1. A steel of low carbon content between .01 and 25% carbon, containing as essential alloying constituents 1.10% to 1.65% silicon, .15 to .60% copper and .10 to 22% phosphorus not over about 5% manganese and not over about .05% sulphur, the balance and characterized by corrosion resistance, strength, ductility and weldability.

2. A steel of low carbon content between .07 and 12% carbon, containing as'essential alloying constituents 1.20 to silicon, .30 to .45% copper, .12 to .15% phosphorus, not over about .5 manganese and not over about .05% sulphur, the, balance being substantially all iron, and characterized by corrosion resistance, strength,

ductility and weldability.

3. A steel of low carboncontent between .01 and 25% carbon, containing as essential alloying constituents 1.20-1.65% silicon, .15-.60% copper,

phosphorus notover about .5% manganese and not over about 05% sulphur, the balance being substantially all iron, and characterized by corrosion resistance, strengths ductility and weldability.

' BYRAMJI D. SAKLATWAILA.

being substantially all iron, 

